System for different bond pads in an integrated circuit package

ABSTRACT

An integrated circuit package is provided with a substrate having first and second contact pads exposed through a passivation layer on the substrate. A first metallurgy layer is over the substrate. A second metallurgy layer is over the first metallurgy layer. A protective layer is over the first contact pad.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This is a Divisional of co-pending application Ser. No. 10/846,176 filedMay 13, 2004, which is hereby incorporated by reference herein.

TECHNICAL FIELD

The present invention relates generally to semiconductor integratedcircuits, and more specifically to integrated circuit packaging.

BACKGROUND ART

With continuously decreasing semiconductor device dimensions andincreasing device-packaging densities, the packaging of semiconductordevices has continued to gain in importance. In the electronicsindustry, the continuing goal has been to reduce the size of electronicdevices such as in digital cameras and camcorders.

In the past, integrated circuits were packaged in leadframe packagesusing wire bonds using metal wires, but the packaging technology hasbeen moving towards ball bond packages using solder balls, which allowfor a higher density of connections.

Because the marketplace is in the process of transition, it is desirableto mix both wire and ball bonds in the same integrated circuit package.

Unfortunately, the requirements for wire and ball bonds are different.For example, aluminum (Al) is typically used for the wires because it isa very easily bent with little springback. Al bonds well to pads of Al.On the other hand, tin (Sn) solder is typically used for the ballsbecause it has a high surface tension for forming small balls. Sn solderbonds well to pads of copper (Cu), which is a very good solderingwettable material.

The above results in the requirement for Al bond pads for wire bonds andCu bond pads for ball bonds. Unfortunately, Al wire does not bond wellwith Cu bond pads and Sn solder does not bond well with Al bond pads.

In the past, Al was used in the final metal pads during integratedcircuit fabrication, and Cu pads were made by thin-film deposition overthe Al pads by an additional step of evaporation or sputtering. Thethin-film layers of Cu are referred to as “under bump metallurgy” (UBM).The UBM plays a critical role as an adhesion layer between Al pads andsolder bumps. To get different metal pads in one integrated circuitpackage, various approaches have been attempted, but have had theproblems of requiring different masks to protect the Al pad in order toobtain a desired UBM.

Solutions to these problems have been long sought but prior developmentshave not taught or suggested any solutions and, thus, solutions to theseproblems have long eluded those skilled in the art.

SUMMARY OF THE INVENTION

The present invention provides an integrated circuit package with asubstrate having first and second contact pads exposed through apassivation layer on the substrate. A first metallurgy layer is over thesubstrate. A second metallurgy layer is over the first metallurgy layer.A protective layer is over the first contact pad.

Certain embodiments of the invention have other advantages in additionto or in place of those mentioned above. The advantages will becomeapparent to those skilled in the art from a reading of the followingdetailed description when taken with reference to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of an integrated circuit package in accordance with thepresent invention;

FIG. 2 is a close-up view of a portion of one of the structure in FIG. 1in an intermediate stage of manufacture according to the presentinvention;

FIG. 3 is the structure of FIG. 2 after deposition of first and secondunder bump metallurgy layers;

FIG. 4 is the structure of FIG. 3 after deposition and patterning of aphotoresist;

FIG. 5 is the structure of FIG. 4 in accordance with one embodiment ofthe present invention after removal of the photoresist;

FIG. 6 is the structure of FIG. 2 after deposition of an input/outputcap layer, and first and second under bump metallurgy layers;

FIG. 7 is the structure of FIG. 6 after deposition and patterning with aphotoresist;

FIG. 8 is the structure of FIG. 7 after deposition and patterning of aphotoresist over the first input/output contact pad;

FIG. 9 is the structure of FIG. 8 after removal of the photoresist; and

FIG. 10 is a flow chart of a method for manufacturing an integratedcircuit package in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1, therein is shown an integrated circuit package100 in accordance with the present invention. The integrated circuitpackage 100 has a package substrate 102 with solder balls 104 on thebottom, and a bottom semiconductor die 106 on the top.

The bottom semiconductor die 106 is wire bonded by wire bonds 108 to thepackage substrate 102. On top of the bottom semiconductor die 106 aretop semiconductor dies 110 and 112 that are ball bonded by ball bonds114.

The bottom semiconductor die 106 and the top semiconductor dies 110 and112 are encapsulated by an encapsulant 116 of a material such as epoxyor plastic. Each of the dies have semiconductor material substrates andmay be connected in different combinations by different combinations ofwire and ball bonds within the integrated circuit package 100.

The term “horizontal” as used herein is defined as a plane parallel tothe conventional plane or surface of the package substrate 102,regardless of its orientation. The term “vertical” refers to a directionperpendicular to the horizontal as just defined. Terms, such as “on”,“above”, “below”, “bottom”, “top”, “over”, and “under”, are defined withrespect to the horizontal plane.

In the following description, numerous specific details are given toprovide a thorough understanding of the invention. However, it willbecome apparent that the invention may be practiced without thesespecific details. In order to avoid obscuring the present invention,some well-known system configurations and process steps are notdisclosed in detail.

Likewise, the drawings showing embodiments of the invention aresemi-diagrammatic and not to scale and, particularly, some of thedimensions are for the clarity of presentation and are shown greatlyexaggerated in the FIGs. In addition, where multiple embodiments aredisclosed and described having some features in common, for clarity andease of illustration and description thereof, like features one toanother will ordinarily be described with like reference numerals.

The term “processing” as used herein includes deposition of material orphotoresist, patterning, exposure, development, etching, cleaning,and/or removal of the material or photoresist as required in forming adescribed structure. The term “forming” as used herein includesprocesses such as depositing, growing, building, chemically combining,or other processes for forming layers, films, and structures.

Referring now to FIG. 2, therein is shown a close-up view of a top orbottom surface of semiconductor die or package substrate in anintermediate stage of manufacture according to the present invention.The semiconductor die could be the bottom semiconductor die 106 or thetop semiconductor dies 110 or 112, or the package substrate 102.

In one embodiment, the top of the bottom semiconductor die 106 includesa portion generically described as a substrate 200. The substrate 200has first and second input/output (I/O) contact pads 201 and 202 exposedthrough a passivation layer 204 thereon.

The first and second I/O contact pads 201 and 202 are generally ofwire-bond pad material such as aluminum (Al), or an alloy of aluminumsuch as aluminum/copper (AlCu). The passivation layer 204 is of adielectric material such as silicon oxide (SiO₂).

Referring now to FIG. 3, therein is shown the structure of FIG. 2 afterdeposition of first and second under bump metallurgy (UBM) layers 300and 302.

The first UBM layer 300 is of a material which is processed or etched byan etchant which will chemically combine with the material of the firstand second I/O contact pads 201 and 202 to form a thin protective layerwhich will prevent further etching of the first and second I/O contactspads 201 and 202 as will be further explained later. For example, forI/O contact pads containing Al, the first UBM layer 300 could be oftitanium (Ti), which is etched with hydrofluoric acid (HF). The HF wouldreact with Al to form a very thin aluminum fluoride (AlF) layer, lessthan 100 Å thick, that acts as a protective layer for the remainder ofthe Al.

The second UBM layer 302 is of a material which bonds well to the firstUBM layer 300. For Ti, the second UBM layer 302 can be nickel vanadium(NiV) or copper (Cu). Both NiV and Cu provide good soldering wettablematerials for ball bonds.

Referring now to FIG. 4, therein is shown the structure of FIG. 3 afterdeposition and patterning of a photoresist 400. The photoresist 400 ispatterned followed by processing or etching removal of the first andsecond UBM layers 300 and 302 from all areas except over the second I/Ocontact pad 202. The etchant used for the first UBM layer 300 is onethat forms a protective layer 402 over the first I/O contact pad 201.

Referring now to FIG. 5, therein is shown the top of the bottomsemiconductor die 106 in accordance with an embodiment of the presentinvention after removal of the photoresist 400 from the second UMB layer302. This structure provides the first I/O contact pad 201, which couldbe of Al, protected by the protective layer 402 and the second I/Ocontact pad 202 having the second UMB layer 302, which could be of Cu.

Referring now to FIG. 6, therein is shown the structure of FIG. 2 afterdeposition of an I/O cap layer 600, a first UBM layer 602 and a secondUBM layer 604. The I/O cap layer 600 is a wire-bond pad materialselected based on the material of the first and/or second I/O contactpads 201 and/or 202 not being the desired material for wire bondingpads, such as Cu. For example, the I/O cap layer 600 can be of pure Al,AlCu, or another alloy selected to bond well to the first and/or secondI/O contact pads 201 and/or 202 and to the first UBM layer 602.

The first UBM layer 602 is of a material which is etched by an etchantwhich will chemically combine with the material of the I/O cap layer 600to form a thin protective layer which will prevent further etching ofthe I/O cap layer 600 as will be further explained later.

For example, it has been discovered that for I/O contact pads containingAl, the first UBM layer 602 could be of Ti, which is etched with HF. TheHF would react with Al to form a very thin AlF layer of less than 100 Åthick that acts as a protective layer for the remainder of the Al duringthe etching of the titanium with a HF etchant having less than 1% HF.The second UBM layer 604 is then of a material which bonds well to thefirst UBM layer 602. For Ti, the second UBM layer 604 can be NiV or Cu.Both NiV and Cu provide good soldering wettable materials for ballbonds. This embodiment of the present invention allows a single mask tobe used to obtain the UBM and protect the Al bond pad.

Referring now to FIG. 7, therein is shown the structure of FIG. 6 afterdeposition and patterning with a photoresist 700. The photoresist 700 isused during the processing or etching of the first and second UBM layers602 and 604. Because of the formation of a protective layer 702 on theI/O cap layer 600 by the etchant used for the first UBM layer 602, theI/O cap layer 600 is not etched.

Referring now to FIG. 8, therein is shown the structure of FIG. 7 afterdeposition and patterning of a photoresist 800 over the first I/Ocontact pad 201 and the I/O cap layer 600. The photoresist 800 for thefirst I/O contact pad 201 and the first and second UBM layers 602 and604 for the second I/O contact pad 202 act as masks for the processingor etching of the I/O cap layer 600.

Referring now to FIG. 9, therein is shown the structure of FIG. 8 afterremoval of the photoresist 800 therein. The I/O cap layer 600 over thefirst I/O contact pad 201 can act as a wire bond pad and the I/O caplayer 600, and the first and second UBM layers 602 and 604 act as a UBMpad for over the second I/O contact pad 202.

Referring now to FIG. 10, therein is shown a method 1000 formanufacturing an integrated circuit package in accordance with thepresent invention.

The method 1000 includes: a step 1002 wherein a substrate has first andsecond I/O contact pads exposed through a passivation layer; a step 1004where a first UBM layer is formed over the package substrate; a step1006 where a second UBM layer is formed over the first UBM layer; a step1008 where the first UBM layer is removed leaving a portion thereof overthe second I/O contact pad; a step 1010 where the second UBM layer isremoved while leaving a portion over the second I/O contact pad; and astep 1012 where a protective layer is formed over the first I/O contactpad while removing the first UBM layer.

While the invention has been described in conjunction with a specificbest mode, it is to be understood that many alternatives, modifications,and variations will be apparent to those skilled in the art in light ofthe aforegoing description. Accordingly, it is intended to embrace allsuch alternatives, modifications, and variations which fall within thespirit and scope of the included claims. All matters set forth herein orshown in the accompanying drawings are to be interpreted in anillustrative and non-limiting sense.

1. An integrated circuit package comprising: a substrate having firstand second contact pads thereon exposed through a passivation layerthereon; a first metallurgy layer over the second contact pad separatedfrom the substrate by the passivation layer; a second metallurgy layerover the first metallurgy layer over the second contact pad andseparated from the substrate; and a protective layer over the firstcontact pad.
 2. The method as claimed in claim 1 wherein: the protectivelayer is a compound of an etchant component reacted with the material ofthe first contact pad.
 3. The method as claimed in claim 1 furthercomprising: a cap layer over the first and second contact pads; andwherein: the protective layer is a compound of an etchant component withthe material of the first contact pad.
 4. The method as claimed in claim1 further comprising: a wire-bond pad semiconductor die or packagesubstrate wire-bonded to the first contact pad; a bump pad semiconductordie or package substrate ball bonded to the second metallurgy layer overthe second contact pad; a semiconductor die or package substrateconnected to the substrate; and an encapsulant encapsulating at least aportion of the substrate.
 5. The method as claimed in claim 1 wherein:the substrate comprises at least one of the first and second contactpads using aluminum, an alloy thereof, or a compound thereof; the firstmetallurgy layer uses titanium, an alloy thereof, or a compound thereof;the second metallurgy layer uses at least one of nickel, vanadium,copper, an alloy thereof and a compound thereof; and the protectivelayer uses aluminum fluoride.
 6. An integrated circuit packagecomprising: a substrate having first and second contact pads thereonexposed through a passivation layer thereon; a first under bumpmetallurgy layer over the second contact pad separated from thesubstrate by the passivation layer; a second under bump metallurgy layerover the first under bump metallurgy layer and separated from thesubstrate; a protective layer over the first contact pad; and additionalsubstrates connected to the substrate by the first and second contactpads.
 7. The method as claimed in claim 6 wherein: the substratecomprises the first contact pad using aluminum, an alloy thereof, or acompound thereof; the first under bump metallurgy layer uses titanium,an alloy thereof, or a compound thereof; and the second under bumpmetallurgy layer uses at least one of nickel, vanadium, copper, an alloythereof and a compound thereof.
 8. The method as claimed in claim 6further comprising: a cap layer over the substrate under the first underbump metallurgy layer, the cap layer uses at least one of aluminum,copper, an alloy thereof, and a compound thereof; and wherein: theprotective layer is a compound of fluorine and aluminum.
 9. The methodas claimed in claim 6 wherein: the additional substrates comprise: awire bond pad semiconductor die or package substrate wire bonded to thefirst contact pad; and a bump pad semiconductor die or package substrateball bonded to the second under bump metallurgy layer over the secondcontact pad.
 10. The method as claimed in claim 6 wherein: theadditional substrates comprise: a package substrate connected to thesubstrate by a wire bond; a further substrate connected to the substrateby a ball bond; and further comprising: an encapsulant encapsulating thesubstrate; and solder balls on the package substrate.